The present invention relates to baffle for a turbine nozzle. In particular, the invention relates to a turbine nozzle baffle for an axial turbine engine.
A turbine engine ignites compressed air and fuel in a combustion chamber, or combustor, to create a flow of hot combustion gases to drive one or more stages of turbine blades. The turbine blades extract energy from the flow of hot combustion gases to drive an engine shaft. The engine shaft drives a compressor to provide a flow of compressed air. The engine shaft may also supply shaft power for use by a fan to provide thrust in a turbofan engine or for use by, for example, an electrical generator. Nozzles ahead of each of the one or more stages of turbine blades contain vanes to align the flow of hot combustion gases for an efficient attack angle on the turbine blades.
In most instances, a portion of the flow of compressed air flows around turbine rotor disks that connect the turbine blades to the engine shaft. This compressed air flow cools the rotor disks before exiting through gaps between adjacent turbine rotors and nozzles and into the flow of combustion gases. The positive pressure of the exiting compressed air prevents ingestion of hot combustion gases into cavities adjacent to the turbine rotor disks.
The turbine rotor disks spin at very high rates, for example, 60,000 revolutions per minute. In doing so, the turbine rotor disks tend to impart a high degree of angular velocity to the compressed air flowing through the cavities adjacent to the turbine rotor disks. This transfer of energy from the rotating turbine rotor disk to the compressed air represents a drag on the turbine rotor disk, resulting in energy loss and engine inefficiency. This drag is known as windage. Uneven surface features along the cavities adjacent to the turbine rotor disks contribute to windage losses. In addition, a large volume of space adjacent to the turbine rotor disk also increases windage losses.